Ferns for Cool Climates

There are a number of Australian native fern species which are relatively easy
to grow outdoors in cool climate areas.

Ferns require good drainage and it is important that some form of protection,
such as overhanging trees, shrubs, a garden wall, the wall of a house or shade
cloth, is provided. Where there are extremes of dry heat and cold, suitable growing
conditions can be developed by enclosing areas sufficiently to keep the humidity
high.

When planning the site for a fern garden, easterly and southerly aspects are preferable.
The majority of ferns grow best in filtered sunlight and although some will tolerate
direct sunlight, they should not be subjected to it for long periods.
Frost damage may occur to fronds, but it will not be as severe if regular watering
is kept up throughout winter. Damage to foliage may also occur during long periods
of dry heat and wind. Damaged fronds will not recover and should be removed.

Preparation of Soil

Ferns generally grow best in slightly acid soils which contain plenty of organic
matter. Good soil conditions can be created by digging to spade depth and incorporating
liberal quantities of coarse peat moss, well-rotted leaf-mould or compost. The
structure of heavy soil may be improved by the addition of gypsum and coarse sand.

Planting

Spring is the best time for planting, although a number of species do equally
well if planted in early autumn. Mulching is important to keep weeds down and
the soil moist. Eucalyptus leaf litter, hardwood shavings, weathered she
oak (Casuarina and Allocasuarina ) needles or oak leaf litter make
good mulches. Mulches should be topped up regularly.

Fertilising

Ferns are gross feeders and fertilisers are best applied during the warm months
when plants are growing. Blood and bone or liquid organic fertilisers such as
fish emulsion are suitable. Iron deficiency is common in ferns and can be corrected
by applying iron chelates to the soil at the recommended rate. Typical symptoms
are yellowing and bleaching of young fronds although, these symptoms may also
occur in areas where there is high light intensity.

Maintenance

Apart from the removal of dead fronds, ferns do not require a great deal of maintenance
and, once established, the soil surface should be disturbed as little as possible.
Daily watering is necessary while plants are young, even during winter. This should
consist of deep soaking about once a week followed by a light daily watering.
During the summer, watering needs to be consistent. Automatic sprinkler and drip
irrigation systems are ideal for this purpose.

Propagation

Some ferns are readily propagated by means such as division of the rhizomes (under
ground stems) or crowns, layering and plantlets. Division is best carried out
just prior to the active growth period in spring. The rhizomes can be cut into
lengths and those with a growing tip can be potted up. Fronds attached to the
divisions may die but new fronds will grow.

Some ferns, such as Asplenium bulbiferum and Polystichum species,
produce small plantlets or bulbils along the stem or on, or near, the tip of the
fronds. Plantlets can be pegged onto the ground and removed from the parent plant
once roots are developed.

Pests

Some common pests of ferns and the method of control are listed. Many ferns, especially
fine-foliaged species, are sensitive to pesticides and care should be exercised
in their application. When using pesticides, safety directions should be followed
carefully.

Caterpillars (late summer) can be are controlled by crushing the animals by hand,
or, in cases of severe infestation, a spray such as Carbaryl" may be applied.

Aphids may attack new fronds especially in spring and autumn and can be controlled
with a contact spray such as those based on Pyrethrum extract.

Scale insects are generally found on stems and on the undersurfaces of fronds.
They may be brushed from the surface using a toothbrush or, in cases of severe
infestation, white oil and 'Rogor 40' or 'Folimat' may be used. Foliage 'burn'
may occur if these pesticides are used when temperatures exceed 25 degrees C.